This invention relates to a liquid addition funnel for reaction vessels having internal pressures different from atmospheric and in particular to a pressure equalizing funnel whereby the pressure above the liquid to be added is the same as that within the reactor.
Chemical laboratories often preform reactions under a variety of conditions which include temperatures and pressures different from ambient. Such reactions then are preformed in closed systems whereby temperature and pressure are interdependent or where pressure alone is a major variable. Pressures exceeding 100 psig are not uncommon.
In such systems the addition of liquid reagents becomes a problem. In the past small expensive high pressure pumps have been used extensively for the introduction of reagents. Flow is controlled by varying the speed or stroke of the unit. Such pumps however do not respond to pressure changes within the vessel and are difficult to regulate when small quantities are involved. The backstroke is the same slow speed as the forward stroke and anti-suck-back valves do not close fast enough or are prone to remain shut, causing erratic flow. There are also presently available liquid addition funnels with external, pressure equalizing tubes which place the interior of the reaction vessel in communication with the interior of the funnel above the liquid to be added. In U.S. Pat. No. 3,370,761 such a vessel is described. While such exterior arms do equalize pressure so that the pressure above the liquid to be added is the same as that in the pressure vessel, such external tubes create a safety hazard when made of glass because of their fragility.
It should be noted that in that patent that a valve stem regulated by rotating a threaded member is used to open or close the outlet to the funnel. In other nonpatented prior art devices having pressure equalizing external tubes a stopcock is used instead of a valve stem. The stopcock however is subject to squirting o "suck-back" which is undesirable.
With the advent of glass threads, connectors, plugs and the like can be provided for glass reaction vessels which permit operation at elevated pressures up to the bursting point of the vessels. See for example U.S. Pat. No. 3,695,642 which describes a variety of connectors, plugs and the like wherein the glass female member has internal threads and preferably a male member is provided with external threads. The male member normally is constructed of polylterafluoroethylene (hereinafter Teflon). Such vessels then can maintain internal integrity at pressures up to and above 200 psig, and in the case of borosilicate glass up to the allowable tensile stress of 1000 psi. According to the disclosure of U.S. Pat. No. 3,695,642 is hereby incorporated by reference.